There are many forms of packaging which require the use of screw caps or closures. Many of these closures require the insertion of a liner in order to obtain proper performance with the final package. These liners are used for various purposes. Some examples are: liquid tight seals, hermetic seals for product protection and seals providing tamper evidence. The liners are generally round in shape, although some may have protrusions for pull tabs or tabs which lock the liner into the closure. Liner materials can vary as well. They can be made of various laminations or of a single material. Some examples are: laminated boardstock, plastic foam, foil and foil laminates.
The machines which cut and insert these liners have usually been of the intermittent motion type. Generally, the caps are lined up beneath the liner material and the liner is punched out of the web and down into the closure. The next set of closures is then indexed into position while the punch retracts and the liner web is indexed forward. Where multiple liners are to be cut from a web, the punches are lined up at an angle to the web, thus maximizing the material usage. While these machines are not complex and do provide good material usage, they do have shortcomings. Because they are based on intermittent motion principles, they have speed limitations. Also, they incorporate precision punch and die systems which require very accurate setup and adjustment. In addition, they require a lot of time to set up when changing from one closure size to another. Further, because of their speed limitations, they cannot exactly match the output of the molding machines which produce the caps or closures. Thus, these machines require a separate department for operation. Caps from the molding machine must be put into intermediate containers, moved to storage, stored, moved to the liner department, emptied, sorted, lined, inspected, placed into the final shipping container and moved to the shipping area. Work in process and inventories can be quite expensive. Also, the floorspace and staffing required for a separate department add cost to the final product.
It is generally visualized that what might solve these problems is to develop a small, high speed, quick change, rotary motion machine to install directly at the closure molding machine; a machine that could both rotary die cut and then insert liners into associated closures, such as screw caps, immediately after closure molding and just prior to putting closures into a shipping container. This would eliminate the need for a separate department along with the associated handling and inventory management of closures waiting for liner inserts.
One previously known way of rotary cutting is to pass a web of material between a pair of superimposed rotating metal cylinders with one cylinder having a plain cylindrical surface acting as an anvil for cutting elements carried by the other cylinder. The cutting elements project generally radially outwardly from the body of the rotary die cylinder and have a sharp knife edge with a V-shaped cross section that penetrates the web and just lightly touches the anvil surface. Such rotary die cutters have been adapted to pick up the cut blanks and carry them on the cutters for "handoff" transfer to an associated inserter post carried on a rotary transfer roll. That post in turn carries the cut blank into registry with an associated closure disposed in a feed chute and then seats the liner in the closure.
However, for proper operation of such a rotary machine, there would need to be an array of liner pick-up transfer and inserter posts on a roll or other conveyor with a reasonable spacing of inserter posts so they can properly "pick" caps from the feed chute. However, in order to obtain maximum web utilization (i.e., minimize the scrap areas between liner cuts), the individual cutting dies would normally need to be spaced very closely together. In the past, to move from a closely spaced liner at the point of cut to a larger spacing at point of insertion would entail the use of "cut and slip" methods. This means there would be relative movement between the cut part and at least one of the rolls adjacent and along the path of travel of the cutter. The cut part would generally be held onto one roll at the initial spacing by vacuum. It would then be transferred to another roll at a different spacing by having the leading edge of the part pulled onto the second roll by stronger vacuum or a combination of vacuum on the second roll with positive pressure blow-off on the first roll. With the second roll traveling a bit faster than the first roll, the part would drag or "slip" on the first roll. This resulted in relatively inaccurate location on the second roll, especially for very small parts. Because of this inaccuracy, continuous rotary processing of small parts which require a variation in spacing from initial cut has heretofore been impossible.